1. Field of the Invention
This invention relates to a tension adjustment mechanism specifically adapted to perform a final tension adjustment to equalize tension in tendon legs of a floating marine platform.
2. Background Art
For offshore drilling operations, it is conventional to moor a floating marine platform by tendons depending from the platform to anchors on the seabed. In such a tendon leg platform (TLP), the tendons hold the platform at a level below its normal buoyancy level in order to reduce vertical buoyant movement of the platform. Therefore, the tendons are put under tensile stress by the buoyancy of the platform.
A final tension adjustment of the tendons of a TLP is usually made after deballasting of the TLP hull. As a result of deballasting, the gross tendon load is applied via vessel buoyancy. A final adjustment to equalize the load in all tendons is made by mechanical means incorporated into a top connector of each tendon. The final adjustment is accomplished by ballasting the TLP to remove load from the tendons, adjusting the lengths of the tendons, and then deballasting again.
The mechanical means used for the final tension adjustment can add a great deal of complexity and weight to the top connector assembly of each tendon. Typically the mechanical means includes a tie-off nut, elastomeric bearing, load ring, adjustment shaft, and corrosion cap. The elastomeric bearing is mounted to the TLP, and the tie-off nut nests upon the elastomeric bearing. The adjustment shaft is threaded and engages the tie-off nut, so that the tie-off nut can be rotated with respect to the adjustment shaft to perform the final tension adjustment.